2012AJ....144..136Y

We present new photometry for the eclipsing binary V1241 Tau, which was obtained on six nights between 2011 December and 2012 January using the 85 cm telescope at the Xinglong station of the National Astronomical Observatories of China. By using the updated Wilson-Devinney code, photometric models with third lights were deduced from two sets of light curves. The result implies that V1241 Tau is an Algol-type near-contact binary (NCB), whose mass ratio and filling-out of the primary are q = 0.545 (± 0.003) and f₁= 82.4% (± 0.2%), respectively. Based on all available times of minimum light spanning over 80 yr, the O - C curve of V1241 Tau appears to show a quasi-sinusoidal oscillation, i.e., a light-time orbit. The modulated period and amplitude are P_mod= 47.4 (± 1.7) yr and A = 0.0087 (± 0.0005) days, respectively. This kind of period variation may be more likely attributed to the light-time effect via a presence of an unseen third body. From an analysis of 23 Algol-type NCBs with EB-type light curves, we determine that the fill-out for the primary f₁ will increase as the orbital period P decreases. With angular momentum loss, the orbit of the binary will shrink, which causes f₁ to increase. The primary component finally fills its Roche lobe, and the binary evolves into contact configuration. Therefore, this kind of Algol-type NCB with EB-type light curves, such as V1241 Tau, may be a progenitor of the A-type W UMa binary.